1. Field of the Invention
This invention relates generally to liquid-solid separators and particularly to portable separators employing a combination of filtration and capillary action for treatment of sludge in bulk.
2. Prior Art
The object of liquid solid separators is to remove the liquid from solids in a sludge. This is desirable for several reasons. First, certain environmental regulations require the water content of solid waste to be below specified levels before it may be accepted in a landfill. Second, such waste must frequently be hauled to the treatment or disposal site, and the freight carriers, as well as the disposal site, often charge by the pound. Finally, in many industrial processes, the finished product will be either a solid or a liquid contained in a sludge, and it will be necessary to separate the solid from the liquid phase in order to isolate the finished product.
One such separator is disclosed in U.S. Pat. No. 4,929,353 by Harris. Harris discloses a phase separator that comprises a tank having a bed and surrounding sides. A grating is supported over the bed and walls leaving a space between the grating and the wall and the bed below. A screen is attached to the grating. A filter is then laid over the screen and grating, and sludge is deposited in the tank on top of the filter. The liquid in the sludge will move through the filter. In Harris, movement from the sludge to the filter is accomplished by gravity, hydrostatic pressure and by wicking, or capillary action. After passing through the filter, the liquid will collect in the space between the bed and the grating. A drain is provided to allow such liquid to be released from the tank. A shortcoming in such a separator is that with many types of sludge, the center portion of the tank either will not dry completely or takes an excessively long time to dry. This results in increased freight charges, lengthy drying times and, occasionally, rejection by landfills.
Another problem faced by those attempting to remove liquids from sludge is "blinding." One cause of blinding is when the liquids pass through the filter rapidly. When this occurs, the finer solids are carried with the liquid to the filter where the solids are deposited. As the solids are deposited, they coat the filter and can substantially inhibit further drainage through the filter.